Quality information diagnosis related to the present invention is presented in Patent literature 1. As shown in FIG. 11 and FIG. 12, such a previous method uses fault tress to diagnose potential component failures with respect to some particular system failures reported by users. This is a typical application of fault tree analysis (FTA) in a top-down way.
However, this method cannot answer the reverse question, that is, what are the current critical components in the occurrences of some other component failures and recoveries at runtime, which is especially a key concern of fault tolerant systems in practice.
Direct applying traditional FTA in a bottom-up way may have troubles to solve the above problem. This is because that the traditional FTA does not consider conditional events (i.e., normal events which are not considered as faults) in the minimal cut sets (MCS), and it may have troubles to handle with sequential dependency between different events due to its simple Boolean logic semantics. To illustrate it, we refer to Non-patent literature 1, in which a minimal cut set is defined as a smallest combination of component failures which, if they all occur, will cause the top event to occur. Here the top event is typically understood as the highest level of undesired system hazard, i.e., the root of the fault tree. Without considering necessary conditional events in the fault tree, such a definition may just fail for the analysis of runtime MCS. Here by runtime MCS we mean the current MCS of the fault tree in the occurrences of some component failures and recoveries, which is important to predict the current critical components of the system at runtime.
Temporal fault trees may help to solve the sequential dependency problem of traditional fault trees, such as the one presented in Non-patent literature 2.
However, if temporal operators have been introduced into the MCS of fault trees, then it may increase the complexity and cost for the calculation of runtime MCS since the sequences rather than combinations of component failures are typically required for consideration.